This invention relates to improvement of fuels and more specifically provides that a supply of energy fuels such as coal may be refined so that combustion with oxygen in air can be accomplished more rapidly than heretofore.
Until recently the smallest coal particles produced by reduction in mechanical mills were usually in the order of 75 microns. By using electro-filters for example particles of 35 microns size have been reached. Although laboratory amounts may be known, commercially usable quantities with a fineness of 5 microns as required by industry have not been universally available.
According to recent developments hereinafter set forth, a fineness of 4 microns can nevertheless be obtained in large amounts commercially, and in accordance with the process of this invention uses such as feed material which is then additionally refined up to 1/300 micron through a purely thermal treatment. The 4 micron size is achieved through a mechanical grinding process, which is described in the transcript of Hearings on S 2806 before the Ninety-Third Congress on Jan. 28, 1974, pages 1632 and 1633 and which are disclosed as known art in German patent 690653, May 3, 1940. This art complements and comprises part of this particular application, and explains how the new 4 micron powders are mechanically produced.
This invention, however, deals with the production of the "ultrafine powder" in the size of 1/300 micron for which the powder of 4 micron size is the feed material. The 4 micron powder that leaves the mechanical reductor mill then falls from above by gravity into an apportioning-chamber-wheel, where it is quantitatively measured and then empties below. By this process the exiting powder is controlled with the help of a revolving gate in such a manner that the 4 micron powder may be withdrawn or it falls vertically from the chamber-wheel into a vertical discharge line below for an additional thermal treatment. This discharge line on its upper end is provided with blow-off holes, through which nitrogen is fed under a small pressure so that the falling 4 micron powder cannot settle on curvatures of the pipe conduit and therefore continues falling.
The vertical discharge line is surrounded with a concentric cylinder housing, in which a helix type passageway is placed adjacent to the discharge line. Through this helix liquid ammonia at minus 77.degree. C is fed upwardly from below. To avoid heating of the ammonia-helix from the outside, the cylinder housing is provided with a jacket, with hollow spaces between the inner and outer cylinder housing tightly filled with glass wool or asbestos so that the outer space heat cannot have any effect on the ammonia cooling. At the top of the housing the ammonia is led out through a separate pipe line and returns to a container.
The falling 4 micron powder is now cooled to minus 77.degree. C. on the bottom part of the discharge line to fall into a second apportioning-chamber-wheel. The space above and below the apportioning-chamber-wheel is sealed so that it is never possible for the powder in the pipe conduits and in the chambers to move backwards nor for the air from the outside to penetrate inside. Thus, the upper 180.degree. circumference of the second apportioning-chamber-wheel is cooled to the temperature of minus 77.degree. C.
The very cold powder, apportioned in the second chamber falls now through a short connecting pipe into a larger thermal chamber, fitted below. The larger chamber has the form of a cylinder, and similarly to the preceding cold chamber, it is also surrounded with an insulation housing. This insulation housing is also filled with glass wool, asbestos or also through a vacuum in the double housing suitable for not allowing the prevailing very high temperature of plus 780.degree. C within the inner cylinder space to flow to the outside.
On the upper end of the thermal cylinder is located an annular space around the outer insulation housing. This annular space is connected with the inner space of the hollow thermal cylinder through multiple small connecting pipes, which are radially arranged, and extend through the insulation housing. Hot nitrogen gas is fed into the hollow thermal cylinder at a temperature of plus 780.degree. C through a sideway-flanged transverse pipe, located at half height. This feeder transverse pipe is bent upwards at 90.degree. in the vicinity of the axis of the hollow cylinder so that its exit is exactly concentric with the feeder pipe for the cold 4 micron powder.
It is important that the feeder pipe for the 4 micron powder is 1.5 times larger in diameter than the feeder pipe for the heated nitrogen, which flows in opposite direction. The distance between the concentrically arranged ends of the two opposing pipes is twice that of the diameter of the feeder pipe for the 4 micron powder. The previously indicated annular space, with the help of the small radially arranged transverse pipes, serves for the collection of the hot nitrogen gas and for the removal of this gas back to a central container. Directly below the gas collection outlets for these radial small pipes are placed two transverse foils, that are provided with very fine 1/2 m/m borings. Between the two foils is a tightly pressed filling of glass-wool arranged in such a manner to serve as a filter for the ultrafinest powder that is being produced by operating gas flowing up from the lower part of the hollow thermal cylinder to the upper annular space.
Two streams meet in the large cylinder space directly and concentrically upon each other:
a. the minus 77.degree. C cold 4 micron powder, and PA1 b. the plus 780.degree. C hot nitrogen,
whereby the fine powder, which comes from above into the gas stream coming from below, is driven towards the wall of the cylinder and at the touch of the minus 77.degree. C cold coal powders with the 780.degree. C hot gas-mass, due to the existence of gas-filled macro-pores in the 4 micron coal, these particles explode, whereby they are torn apart into the "ultrafinest coal" of the size 1/300 micron. According to experience and many tests, at the conclusion of this process 97.3% of the feed material from the mechanical reductor mill is converted to the ultrafinest coal of 1/300 micron.
At the bottom of the large thermal cylinder is a compactor, whose function is to pack the very fine powder from the large cross section of the thermal container to a sufficiently small stream so that it can be fed to storage.
The compactor consists basically of a funnel like housing, which is attached to the thermal cylinder with a screw flange. On the outside of this funnel in the transverse direction to the main axis of the device are two transverse tubes placed one above the other for the bringing in of nitrogen, which serves as a blow and conveyor means for the very fine powder.
The funnel like housing is assembled from various conical rings with the smallest ring fastened near the bottom of the conical cast funnel housing with a solid socket. A series of progressively larger rings, one following the preceding one, and steadily growing in size, and concentrically arranged so that the uppermost and largest ring has an inner diameter extending to the wall of the large thermal cylinder. The various conical inset-rings in the conical funnel housing are firmly attached to insure against their dislocation. All the conical inset-rings have milled grooves on the outside gas passage holes at the smallest diameter (lower) end allowing gas flow upwardly from smaller to larger rings. Also in the vicinity of its upper and largest diameter each ring has, over its entire circumference, a quantity of small equally spaced borings through which likewise nitrogen under small pressure passes between two rings. The nitrogen is blow inside into the funnel space so that the powder cannot settle on the inner conical spaces of the rings, and so that the falling powder is blow into the funnel toward the smallest conical ring. There in the narrowest part of the last conical ring, through a great number of the smallest borings, a real sieve has been produced through which nitrogen streaming in from the outside is continually blown so that no powder can settle down in the throat of the cone but is always blown out downwardly.
Below the compactor is built, in a separate housing, an apportioning wheel, respectively the third such wheel in such a way that the ultrafine powder is now seized from this wheel and is led to the eventual storage place. The third apportioning wheel conducts the falling powder from the compactor into the outlet tube below the apportioning wheel, from where, by means of nitrogen, it can be transported at will to any distance.
In the third apportioning wheel, through corresponding borings and slits, the powder that falls in from the apportioning chambers can be blown out so that each chamber can be flushed out. It must still be pointed out that all the three apportioning wheels have the same diameter in size, same sized powder chambers and same number of revolutions. To achieve this goal all three chamber-wheels are driven with the same V-belt. It should additionally be pointed out that each apportioning conveyor wheel both in the inflow and outflow direction against the nearest machined parts is completely gas sealed so that the various adjacent spaces and ducts are completely sealed regarding pressures and quantities.
When on the upper end of the entire device the before mentioned reducing mill is mounted, raw coal in the size of 25 m/m (nutcoal IV) is reduced to 4 micron size, the coal that has to be processed can be comminuted up to the size of 1/300 micron in one single throughput so that the entire process will be extraordinarily economical.